Introduction
The existence of God is the central issue in the paradigm of theistic and atheistic traditions. In his fundamental works, Summa Theologiae and Summa Contra Gentiles, St. Thomas Aquinas presented five proofs or ways to prove his understanding of natural theology. Namely, he discussed the concepts of motion, efficient cause, possibility/necessity, gradation, and design to prove the existence of God.
Since the medieval times, the prevailing scholarly view has been that these demonstrations are substantial, standalone arguments discussed by relevant thinkers, such as Kant and Descartes. However, Aquinas’ five ways should be seen as a cohesive, unified theory rather than individual proofs, because they lack the accessibility and validity to prove God’s existence separately. To confirm this thesis, the current paper provides a thorough theoretical overview, defends the position via three critical arguments, and refutes one potential objection.
Theoretical Overview
Five Proofs
A brief introduction to each proof is essential for subsequent analysis and for identifying relevant commonalities between the arguments. St. Thomas Aquinas introduced and elaborated on the five ways in Summa Theologiae and Summa Contra Gentiles. They follow the Aristotelian tradition, emphasizing the core principles of natural theology, such as the idea of motion.
In short, Aquinas explains that nothing can move itself due to the distinction between potentiality and actuality, and, therefore, there must be the “first mover,” who is God. The second way follows a similar premise, stating that nothing can be an “efficient cause of itself,” implying that there must be an entity that could be categorized as the first efficient cause. Aquinas continues this rationale process, further explaining that God is a necessary being, as opposed to contingent ones (third way), and God is the superlative element of gradation (“the most good” model of comparison, fourth way). Lastly, Aquinas states that God exists by design, fulfilling the role of guiding all natural bodies toward their end. Ultimately, these five ways constitute the definitive proof of God’s existence.
The five examined ways are core arguments of natural theology that have been criticized since Aristotle. In Summa Contra Gentiles, Aquinas provides further evidence to support his claims, such as the proof that the first mover should exist and that there cannot be an infinity of movers. He actively references Aristotle and Plato, refuting and confirming multiple claims about theistic principles to rationalize his perspectives on God’s existence. Aquinas’ arguments in Summa Contra Gentiles and Summa Theologiae are pervasive and cannot be overviewed in detail in a single paper. However, it is critical to understand the rationale for the five ways to identify commonalities and to confirm that they constitute a unified theory.
Unified Theories and Standalone Arguments
Consequently, it is imperative to define the primary differences between cohesive theories and standalone arguments to prove that Aquinas’ five ways belong in the former category. It is a challenging task, and even experts with extensive knowledge have their doubts. For instance, Joseph Owens states, “‘Five ways’ are puzzling <…> They do not make clear whether there is more than one or just one proof.” This notion is critical to the current work, as it seeks to provide tangible proof that Aquinas’ five ways constitute a unified theory. However, multiple challenges and barriers may obstruct this goal.
Moreover, the distinction between an integral theory and an individuated proof is loose. Owens explains that fivefold groupings in Summa Contra Gentiles and Summa Theologiae are substantially different from each other, making categorization more complicated. On this topic, Schroeder-Heister believes that individual proofs lack identity or are insufficient to prove their theses independently. In a broad sense, they are incomplete or cannot fully realize their explanatory potential without additional notions.
On the other hand, a cohesive theory is a framework that fully confirms its thesis, and whose sub-elements share commonalities that contribute to the overall explanation. Owens suggests that, since Aquinas’ five ways emerged from various thinkers, including Aristotle and Plato, these arguments have been insufficient on their own, making an integral theory more suitable for proving God’s existence.
Moreover, Aquinas organizes these notions of natural theology into fivefold groupings, suggesting that he personally believed each statement provided sufficient evidence when combined with the other four ways. This perspective is generally consistent with relevant thinkers, who tend to analyze Aquinas’ five proofs together without omitting any presuppositions. Although some authors explicitly discuss individuated proofs, the perspective of a unified theory appears to prevail in scholarly works.
Following this rationale, it might be plausible to confirm that Aquinas’ five proofs comprise a unified theory by proving that one of the statements is insufficient on its own. In other words, if it is possible to refute one of the proofs as an individuated argument but impossible to deny it as a part of a conjunct theory, then Aquinas’ five ways should be perceived as a unified framework. Alternatively, it might be plausible to assess the persuasive power of each proof separately and the unified theory to decide whether it is more practical to understand Aquinas’ five proofs as a cohesive theory or standalone statements.
Common Elements
Lastly, within the scope of the theoretical overview, it is possible to analyze the commonalities of Aquinas’ five ways in the attempt to rationalize the fivefold grouping. First, as Park rightly notes, all five proofs have “naturalistic foundations,” meaning that Aquinas first discusses them in the empirical context rather than in theology. They have manifestations and connections to real-life phenomena, such as motion, causality, possibility, gradation, and teleology. In this discussion in Summa Theologiae, the theological concept of God appears secondary, operating on a different plane of faith, as Aquinas himself notes. However, the five ways employ logic and real-life premises, eventually concluding that only one highest natural cause, described as God, can be the first mover, the first cause, and other respective entities.
Secondly, it is indisputable that Aquinas utilizes the same logical approach to explain the five ways, which is a posteriori, meaning that Aquinas derives knowledge from effect. It is the opposite of a priori, which focuses on cause, even if humans cannot comprehend the cause of God, since, as Aquinas writes, the existence of God is not self-evident. Therefore, the only way to prove this theological argument is to draw a conclusion based on observable manifestations of God’s effects, such as the five ways. The only potential exception to this rule is the fifth proof, which suggests that all natural bodies act towards their end by design, although Aquinas does not perceive it as an a priori argument.
Analysis
Issue of Theological Intent
Having identified the theoretical background for the current work, the next step is to demonstrate that the five ways constitute a unified theory. The paper utilizes three core arguments to achieve this goal: theological intent, the issue of cosmology, and the insufficiency of individuated proofs (namely, the first way). The former suggests that all five ways were formulated with one goal: to create the foundation for subsequent discussion, or, as Aquinas calls it, “preambles to the articles.”
In a broad sense, each individuated proof does not pursue the objective of confirming God’s existence but instead introduces the narrative of consequent articles. Aquinas clearly defines this distinction: “The existence of God and other like truths about God <…> are not articles of faith, but are preambles to the articles.” Therefore, the five ways include a comprehensive introduction to the theological narrative, as further discussed in the Summa Theologiae and the Summa Contra Gentiles. In the context of this work, it suggests that all five proofs share the same theological intent and, since they have the same goal, it is more appropriate to understand them as a cohesive theory rather than as individual proofs.
Issue of Cosmological Arguments
Each of the five ways assumes a cosmological perspective, meaning that their primary focus is explaining the universe rather than a particular cause. In this sense, although Aristotle and Aquinas discuss different Gods, they utilize the same cosmological approach to rationalize their perspectives, such as the unmoved mover. These commonalities between the five ways and Aquinas’ approach, and Aristotle’s further support, strengthen the idea that this discussion is logical in nature, as mentioned briefly before.
Alternatively, assuming that Aquinas truly wanted to prove God’s existence theologically, as he mentions in the Summa Theologiae, it is safe to suggest that he had to differentiate his position from Aristotle’s. Otherwise, the first proof would take the same form as Aristotle’s unmoved mover in his metaphysics, which did not explain the Christian God but rather the laws of the universe through the essence and existence. In this sense, if one perceives Aquinas’ first proof as a standalone argument, it is impossible to draw definitive connections to God because God is not necessarily equal to the highest natural cause outside of the scope of Christianity.
This argument has some flaws because Aquinas lived during a period when the notion of God was immensely prevalent, meaning that God was the creator and the highest natural cause. Allegedly, for most people at that time, the concepts of God and his intentions were evident and self-explanatory. However, judged from a modern perspective, the five ways require additional context and work better in combination. For this reason, Fogelin states that the first three cosmological arguments “do not have the accessibility suggested by their standard appearance in introductory philosophy anthologies.” In the context of the present paper, it is a substantial argument to perceive the five ways as a unified theory today. At the same time, it is a weaker proof to understand the statements as a fivefold group in the period of Aquinas’ work.
Issue of Insufficiency
Having confirmed that the five ways have identical theological intent and lack accessibility on their own, the last step is to establish their insufficiency as standalone arguments for proving God’s existence. The first and most evident proof of this phenomenon is that Aquinas discussed them together in the same article. Authors such as Owens and Kenny argued that this fivefold grouping stemmed from the weaknesses of each individuated proof, suggesting that these proofs were insufficient as standalone arguments. Sir Anthony Kenny, in particular, wrote that the first approach rested on a false presupposition and would not be convincing within the framework of modern scholarly understanding.
Secondly, contemporary physics and the theory of relativity show that the first proof indeed contradicts the natural laws confirmed by Newton and Einstein. While authors primarily focus on Aristotle’s interpretation of the “Primium Mobile,” Aquinas’ first proof is also flawed in the framework of Newtonian mechanics. In the context of the present paper, it is critical since the first way is insufficient proof to confirm God’s existence as a standalone statement. In turn, it means that the other four ways are necessary to enhance the validity of Aquinas’ view that God exists. In the end, it is more fitting to consider the five ways as a single, cohesive theory rather than separate arguments, because none of them alone is enough to establish God’s existence.
This conclusion is the thesis of the present paper, and some relevant authors appear to share this position. For instance, Owens writes about the five proofs, “They are accordingly five different ways of incorporating the one basic demonstration.” This notion mainly supports the argument about theological intent, showing that a cohesive theory is more successful as a preamble for consequent discussion. Sir Anthony Kenny adds, although with a different focus, “It is much more difficult than at first appears to separate [the Five Ways] from their background in medieval cosmology.” This quote primarily concerns insufficiency, as Kenny criticized the five proofs’ false premises according to contemporary scientific standards, calling for the renovation of Aquinas’ five ways. In summary, there is sufficient evidence to suggest that Aquinas’ five proofs should be comprehended as a unified theory, and this approach might further the understanding of Aquinas’ work.
Counterargument
Objection
The paper’s primary argument (insufficiency) builds on the assumption that contemporary science is advanced and that it is common knowledge that some of Aquinas’ proofs rest on false premises. Hence, they might be lacking persuasive power as standalone arguments to convince modern readers that God exists entirely. Nevertheless, this discussion is immensely complex and primarily theological, meaning that flawed logical premises do not necessarily imply that arguments are flawed. It is the principal objection to the present thesis, and many authors believe that Aquinas’ five proofs have immense theological value even as individual arguments.
The primary evidence for this objection is that, while some authors treat the five ways as a fivefold grouping, many experts provide detailed analyses of individual proofs. For instance, Moraes focuses explicitly on the first way as one of the most discussed cosmological statements and refutes Kenny’s claim that the five ways need to be renovated.
Similarly, Fogelin believes that both medieval and contemporary sciences are incapable of explaining all natural causes in detail and, therefore, the argument of insufficiency is less valid. In other words, these authors believe that even individuated proofs provide valuable information both about the theological and cosmological nature of the world. Therefore, there is no need to classify them as a unified theory due to the vast contribution of each separate element.
Response
The objection mentioned is a notable perspective in scholarly literature; however, authors who adhere to this position typically emphasize slightly different aspects of Aquinas’ five ways. Namely, they believe that each individuated proof is valuable, but they do not necessarily oppose the idea of grouping them in a unified theory. Instead, they emphasize that the proofs are valuable regardless of their representation in the narrative, theological intent, or potential flaws in the premises. Even authors from other fields, such as physics, comment that Aquinas’ ways might be flawed “from a mechanical standpoint,” but it does not diminish their significance. In this sense, the first part of the objection has only an indirect connection to the present thesis, as it only concerns the issue of insufficiency but does not refute the statement about a unified theory in general.
Secondly, Fogelin and Moraes refute the claim that the first way’s false premise is due to differences between modern and medieval sciences. However, the present paper responds that it is more appropriate to understand philosophical and theological theories through the prism of contemporary understanding of the world. Evidently, Aquinas’ five ways are valuable even without additional context; however, they inevitably lose some of their argumentative power due to external factors, such as the differences between contemporary and medieval sciences.
Moreover, the paper argues that the primary objective of philosophical tractates is to enlighten others, and that a unified theory of the five ways is more likely to achieve this goal than individuated proofs. Aquinas himself writes, “Now of all human pursuits, that of wisdom is the most perfect, the most sublime, the most profitable, and the most delightful.” Hence, it would be most ethical to view Aquinas’ five ways in the context of modern science, as this could lead to greater wisdom among contemporary readers. The present paper responds to the objection by proving that the difference between today and medieval sciences is crucial. In this context, the counterclaims appear insufficient because they emphasize absolute theological value regardless of the readers.
Conclusion
The present essay critically analyzes Aquinas’ five ways to prove God’s existence and argues that they should be understood as a unified theory rather than individual statements. The three fundamental arguments supporting this position are the theological intent (the same goal in all ways), the flawed connection between cosmology and theology, and the insufficiency of standalone proofs. Among them, the most critical is that the first way fails to confirm God’s existence in the context of contemporary science, meaning it might not serve its purpose when introduced to modern readers. Therefore, it should be supplemented by other Aquinas’ proofs and perceived as a cohesive framework that is substantially more valid and reliable.
Furthermore, this argument is applicable across different settings, as it highlights the significance of wisdom and relative knowledge rather than absolute theological value. For instance, this approach could be used to categorize (and potentially unite as cohesive theories) other Aquinas’ statements found in the Summa Theologiae and the Summa Contra Gentiles. Ultimately, the current essay has confirmed the thesis and established a valuable framework for analyzing theological and philosophical tractates.
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